At the begining of 2013 I've bought KORG LP-350. I practiced every day and all things were great. But today I've swithed on my piano and didn't hear any sound. To be more precise after some time several keys begin to play sound but this sound is wrong. For example keys from the right part of keyboart sound like I've pressed bass and treble note simultaneously. Sometimes after swithing piano on the whole keyboard doesn't work but if I press key on it's right part several times the harsh loud sound is occured.

Example:
http://www.fotografia.com.ua/wp-content/uploads/2013/01/korg350.m4a

You can hear as I switch piano on, then press the key several times without any sound, then harsh sound, then wrong sound of keys from right side of the keyboard.

If I press and don't relese several keys (4-5) simultaneously after 2-3 seconds harsh and chaotic sounds are occured:

http://www.youtube.com/watch?v=k2qOTJ9jDk4

Maybe somebody can help? What's wrong with piano.

P.S. Sorry for possible mistakes. English is not my native language.

It's got a fault. Since you only just bought it, you can get it repaired or replace under warranty. That is the road you should take. We can't really guess what the problem is, nor can we fix it. I'm sure it will be repaired properly if you contact your dealer where you bought it. Good luck.

Try a factory reset, then call the dealer and ask for a replacement.